Patent GB-503388-A (GB)
Title: Alarm signalling systems for repeater stations
IPC: H04Q1/26
Filed: 1938-08-02
Abstract: 503,388. Repeating systems. STANDARD TELEPHONES & CABLES, Ltd. Aug. 2, 1938, No. 22842. Convention date, Aug. 31, 1937. [Class 40 (iv)] [Also in Group XXXVIII] Alarm signals are sent from an unattended telephone repeater station to a main station by a'current variation in a circuit over the line connecting the two stations, a particular signal being identified by the point at which it occurs during the cycle of two synchronous rotary switches at the two stations. As shown, a signal is initiated by the grounding of one of wires 18, 134, 146, 150 which are connected to terminals of switch Sa at the unattended station, Fig. 1. Signals are sent over. a loop including relays 35, 36 and resistance 37 at the unattended station and relays 38, 39 at the main station, Fig. 2, by short-circuiting resistance 37 in order to operate relay 39 which is marginal. The failure of a rectifier, for example, connects up relay 3, and relays 9, 10 operate after a delay period to ground wire 18. Start relay 12 energizes and connects up 20, 24, the latter relay short-. circuiting resistance 37 to send a general alarm signal. Relay 39 responds and short-circuits 42 which is normally operative, whereupon lamp 56 and bell 57 are connected up by relay 52 and start relays 45, 60 pull up. A relay interrupter 69-73 now operates to apply ground pulses to wire 74, and these are repeated to magnet 94 of switch Sm by 40, 49. Relay 40 also opens the loop, so that the pulses are repeated by 35, 79, 80 to magnet 85 of switch Sa. Offnormal relays 27, 47 pull up and the former disconnects 24, so that 42 re-operates. When switch Sa reaches the marked terminal, relay 24 re-operates in series with 17 and again short-circuits resistance 37. Relay 42 is again short-circuited and a circuit is made over switch Sm for relay 102, which locks and. lights lamp 105. In the last position of the switches, 59, 88 operato and direct the next pulse to release magnets 106, 113. Relay 107 disconnects 60 to stop the relay interrupter. Relay 107 disconnects 60 to stop the relay interrupter. Relay 17 upon operating locks and disconnects 12, 20 so that a fresh cycle is not started unless a fresh alarm signal'has been initiated while switch Sa was off-normal. The failure of a transmission regulator connects up relays 131, 9, 10 to ground wire 134. On failure of the power, the relapse of 141 connects up 143, 9, 10, 6 and the last relay disconnects 3, 131 (which necessarily pull up in this case) and grounds wire 146. On restoration of the power, the re-operation of 141 grounds wire 150 without delay. The corresponding signals control lamps 137, 149, 152 at the main station. The nature of a failure may be ascertained at the unattended station by means of lamps 7, 133, 142 which are connected. up by a key 8. Should the signalling loop be open, the relapse of 35 causes switch Sa to step and release alternately and prepares a circuit for lamp 9. At the main station, the relapse of 38, 77 brings about the operation of lamp 56 and bell 57, but stopping of switch Sm may be prevented by depression of release key 54. Actuation of re-check key 67 connects up 30 which unlocks the lamp relays. such as 102 and reverses the current over the loop to operate polarized relay 36, whereupon 90 energizes and unlocks the relays such as 17, so that the signal is repeated. Switches Sa, Sm if off-normal are restored. Modification Fig. 3 (not shown). The signalling circuit comprises a single wire to which a high voltage battery is normally connected at the unattended station, and signals are sent by the substitution of ground to release a normally operated relay at the main station. The pulses for stepping switch Sa are sent by the connection of a lower voltage battery to operate a differential relay at the unattended station.